%I M0211 #18 Jul 25 2019 12:26:13
%S 1,1,2,2,2,2,2,2,4,2,2,2,4,4,2,2,2,2,4,2,2,4,2,2,2,4,4,4,4,2,2,4,4,2,
%T 4,2,2,4,2,2,2,4,8,2,2,4,2,4,2,2,4,4,4,2,2,4,4,2,4,2,2,4,2,2,4,8,2,4,
%U 2,4,4,2,2,4,4,4,4,2,2,2,4,2,4,2,4,8,4,2,4,2,4,4,2,2,4,2,4,4,2,4,4,4,2,2,4
%N Number of genera of imaginary quadratic field with discriminant -k, k = A191483(n).
%D D. A. Buell, Binary Quadratic Forms. Springer-Verlag, NY, 1989, pp. 224-241.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H <a href="/index/Qua#quadfield">Index entries for sequences related to quadratic fields</a>
%F a(n) = 2^(omega(A191483(n)) - 1). - _Jianing Song_, Jul 24 2018
%t 2^(PrimeNu[Select[Range[1000], Mod[#, 4] == 0 && SquareFreeQ[#/4] && Mod[#, 16] != 12&]] - 1) (* _Jean-François Alcover_, Jul 25 2019, after _Andrew Howroyd_ in A191483 *)
%o (PARI) for(n=1, 1000, if(isfundamental(-n) && n%2==0, print1(2^(omega(n) - 1), ", "))) \\ _Andrew Howroyd_, Jul 24 2018
%Y Cf. A001221 (omega), A003640, A003641, A191483.
%K nonn
%O 1,3
%A _N. J. A. Sloane_, _Mira Bernstein_
%E Name clarified by _Jianing Song_, Jul 24 2018